WO2020075967A1 - Dodecyl sulfate-doped poly(3,4-ethylenedioxythiophene) film and manufacturing method therefor - Google Patents

Abstract

The present invention relates to a dodecyl sulfate-doped PEDOT film and a manufacturing method therefor, the method comprising: coating, on a substrate, an oxidizing agent film comprising a dodecyl sulfate metal salt such as Fe(DS)₃; and forming a PEDOT film by a vapor phase polymerization method. The dodecyl sulfate-doped PEDOT film according to the present invention has excellent electrical conductivity so as to be capable of replacing a metal, and has excellent mechanical durability, light transmittance and aqueous solution stability.

Description

Dodecyl sulfate doped poly (3,4-ethylenedioxythiophene) film and method for manufacturing the same

This application claims the benefit of priority based on Korean Patent Application No. 2018-0120286 filed on October 10, 2018, and all contents disclosed in the literature of the Korean patent application are included as part of this specification.

The present invention relates to a PEDOT film having excellent properties and a method for manufacturing the same, and more particularly, to a PEDOT film doped with dodecyl sulfate and a method for manufacturing the same.

Organic conductive materials (organic conductive material) is attracting attention as an electrode material of various electronic devices, including flexible devices (flexible device) due to the characteristics of flexibility, light weight, low cost. In order for the organic conductive material to be used as an electrode material, high electrical conductivity is required. However, among the conductive polymers, only a few are actively studied, and poly (3,4-ethylenedioxythiophene) (hereinafter referred to as 'PEDOT') is a representative material.

PEDOT has a small band gap energy of about 1.5 to 1.7 eV, is transparent, and has excellent thermal stability and stability in the air, so organic transistors, photovoltaic devices, displays, and organic light emitting diodes (OLEDs) It is attracting attention as a transparent flexible electrode of various devices.

The methods of forming the PEDOT film include electropolymerization (EP), vapor-phase polymerization (VP), and solution casting polymerization (SCP). Among them, the electropolymerization method has a limitation that it can be coated only on a conductive surface, and the solution-casting polymerization method requires a high level of technology to obtain a homogeneous film, and the pot life of the polymerization mixture is short, so that it is 10 to 20 minutes. Later, there is a problem that insoluble PEDOT aggregates are formed in the solution. On the other hand, the gas phase polymerization method is a method of polymerizing on a substrate coated with an oxidizing agent by vaporizing EDOT, a monomer of PEDOT, and has the advantage of being able to obtain a high purity homogeneous PEDOT film relatively easily. In addition, it has been reported that the PEDOT film obtained by the gas phase polymerization method is generally superior to the case of using other methods.

However, the electrical conductivity of the PEDOT film reported to date is not enough to replace the metal electrode, and it is recognized as an important task to further improve the electrical conductivity of the PEDOT film. Further, in order to apply the PEDOT film to a flexible device, a display, a bio device, etc., mechanical durability, visible light transmittance, aqueous solution resistance, etc. must also be secured.

On the other hand, in the formation of a PEDOT film by a gas phase polymerization method, the oxidizing agent plays a very important role as a polymerization initiator, and anion of the oxidizing agent is a key material acting as a dopant for the polymer. Known oxidizing agents include FeCl ₃ , H ₂ O ₂ , CuCl ₂ , HAuCl ₄ , Fe (III) Tosylate (Fe (Tos) ₃ ), iron (III) fluoromethanesulfonate (Fe (OTf) ₃ ), iron (III) There are fluride (FeF ₃ ), etc., but these oxidizing agents are highly reactive and crystallize easily, making it difficult to efficiently control the polymerization and reaction of PEDOT and generate defects in the film, making it unsuitable as an oxidizing agent for forming a high-quality PEDOT film. In addition, easily crystallized oxidizing agents have limitations in synthesizing a high-conductivity polymer film because they prevent efficient doping of oxidant anions when the polymer film is grown.

Inhibitors, such as diurethanediol (DUDO), poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) (PEG-PPG-PEG), to lower the high acidity and control reactivity Is usually used, but in this case, there is a problem that the inhibitor remains in the PEDOT film, adversely affecting the electrical conductivity and film stability. Therefore, there is a need for a new oxidizing agent capable of forming a highly stable PEDOT film with a high electrical conductivity by gas phase polymerization without additives such as inhibitors.

The present invention aims to solve the conventional problems as described above, and an object of the present invention is to provide a PEDOT film having excellent electrical conductivity to replace a metal electrode.

In addition, another object of the present invention is to provide a PEDOT film having excellent mechanical durability, flexibility, visible light transmittance, and aqueous solution resistance.

In addition, another object of the present invention is to provide a method capable of forming a high quality PEDOT film.

Another object of the present invention is to provide a novel oxidizing agent and a method for synthesizing the PEDOT film suitable for gas phase polymerization without adding an inhibitor.

PEDOT film according to an embodiment of the present invention is characterized in that the dodecyl sulfate (Dodecyl Sulfate) is a PEDOT film contained as a dopant. The PEDOT film may be formed by a gas phase polymerization method using a dodecyl sulfate metal salt as an oxidizing agent, and the dodecyl sulfate metal salt may be Fe (DS) ₃ . The PEDOT film may be formed as an electrode of an electronic device.

The content of dodecyl sulfate dopant may be in the range of 5-50%. Here, the PEDOT film may be a lamellar structure in which one or more, preferably two dodecyl sulfate molecules are doped between PEDOT molecular layers.

In addition, the PEDOT film according to an embodiment of the present invention may have an electrical conductivity of 5,500 S / cm or more, preferably 10,000 S / cm or more.

In addition, the PEDOT film according to an embodiment of the present invention may exhibit a light transmittance of 90% or more for a wavelength of 550 nm at a thickness of 20 nm.

In addition, the PEDOT film according to an embodiment of the present invention may have an electrical resistance change of 9% after 300,000 bending cycles, or a change in electrical resistance of 10% or less after 30% stretching.

In addition, the PEDOT film according to an embodiment of the present invention may have a change in electrical resistance of 5% or less even after being immersed in deionized water for 20 days or more.

PEDOT film production method according to an embodiment of the present invention, coating an oxidant film containing a dodecyl sulfate metal salt on a substrate, forming a PEDOT film by a gas phase polymerization method on the substrate coated with the oxidizer film, the PEDOT And washing and drying the film. The dodecyl sulfate metal salt may include Fe (DS) ₃ . In addition, the PEDOT film production method according to an embodiment of the present invention may be that does not use an inhibitor.

An oxidizing agent production method for use in preparing a PEDOT film by a gas phase polymerization method according to an embodiment of the present invention comprises the steps of depositing a dodecyl sulfate metal salt by a recrystallization method, washing the precipitated dodecyl sulfate metal salt and vacuum freeze It characterized in that it comprises a step of drying. The dodecyl sulfate metal salt may include Fe (DS) ₃ .

Here, the step of depositing the dodecyl sulfate metal salt by the recrystallization method may further include removing impurities by a centrifugation method.

In addition, the step of depositing the dodecyl sulfate metal salt by the recrystallization method may include preparing a sodium dodecyl sulfate solution and adding FeCl ₃ to the sodium dodecyl sulfate solution. In addition, the step of preparing a methanol solution by dissolving the precipitate generated in the sodium dodecyl sulfate solution in methanol by the addition of FeCl ₃ and precipitation of Fe (DS) ₃ recrystallization by adding deionized water to the methanol solution It can contain.

The PEDOT film according to another embodiment of the present invention is a PEDOT film having a lamellar structure in which at least one anion molecule is doped between PEDOT molecular layers, wherein the anion molecule is CH ₃ (CH ₂ ) _n having a hydrocarbon chain length of 8C to 18C. SO ₄ (n = 7 to 17) is characterized by being a dopant anion. Here, there may be two anion molecules doped between the PEDOT molecular layers.

According to the present invention, by doping dodecyl sulfate on the PEDOT film, there is an effect that can provide a PEDOT film having excellent electrical conductivity to replace the metal electrode.

In addition, according to the present invention, there is an effect that can provide a PEDOT film excellent in mechanical durability, flexibility, visible light transmittance, aqueous solution resistance.

In addition, according to the present invention, by using a gas phase polymerization method using a dodecyl sulfate metal salt such as Fe (DS) ₃ as an oxidizing agent, it is possible to provide a method capable of forming a high-quality PEDOT film without using an inhibitor.

In another aspect, the present invention, there is that by using the Fe (DS) Synthesis of ₃ freeze-drying, to provide an available high-purity, high-quality Fe (DS) ₃ oxidizing agent used in the gas-phase polymerization PEDOT film effect.

1 is a view for explaining a method of forming a dopedyl sulfate doped PEDOT film according to the present invention.

2 is a flowchart of a method for forming a PEDOT film doped with dodecyl sulfate according to the present invention.

3 is a flow chart showing a method for preparing a dodecyl sulfate metal salt oxidizing agent according to the present invention.

4 is a flow chart showing a method of manufacturing a FeCl ₃ oxidizing agent according to an embodiment of the present invention.

5 is a TGA analysis result of Fe (DS) ₃ oxidizing agent prepared according to an embodiment of the present invention.

6 is a DSC analysis result of Fe (DS) ₃ oxidizing agent prepared according to an embodiment of the present invention.

7 is a result of heat treatment at 100 ° C Fe (DS) ₃ oxidizing agent prepared according to an embodiment of the present invention.

8 is a morphology observation result of a PEDOT film formed according to an embodiment of the present invention.

9 is a result of measuring the electrical conductivity of the PEDOT film formed according to an embodiment of the present invention.

10 is a graph of light transmittance at a wavelength of 550 nm according to the thickness of a PEDOT film formed on a PET substrate.

11 is a result of XPS analysis of (a) Fe (DS) ₃ oxidizer film and (b) PEDOT film.

12 is a result of measuring the mechanical properties of the PEDOT film according to an embodiment of the present invention.

13 is a result of measuring the change in sheet resistance over time by immersing the PEDOT film in accordance with an embodiment of the present invention in deionized water.

14 is an in-plane XRD and out-of-plane GIWAXS analysis results of a dodecyl sulfate doped PEDOT thin film according to an embodiment of the present invention.

15 shows the crystal structure of a dodecyl sulfate doped PEDOT film according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. The following description includes specific embodiments, but the invention is not limited or limited by the described embodiments. In the description of the present invention, when it is determined that a detailed description of known technologies related to the present invention may obscure the subject matter of the present invention, the detailed description will be omitted.

The present inventor found that in the process of conducting a study for forming a PEDOT film having a high electrical conductivity that can replace a metal electrode, a very high electrical conductivity is obtained when dopedyl sulfate is doped on the PEDOT film. It came to the invention. In particular, the dodecyl sulfate-doped PEDOT film according to the present invention is not only excellent in electrical conductivity, but also in mechanical durability, visible light transmittance, and aqueous solution resistance, and thus can be successfully applied to various flexible devices and bio devices such as flexible displays.

In addition, the present invention discloses a manufacturing method for forming a PEDOT film having such excellent properties. The PEDOT film production method according to the present invention includes a method for forming a film by a gas phase polymerization method using a dodecyl sulfate metal salt as an oxidizing agent, and a method for manufacturing an excellent quality dodecyl sulfate metal salt oxidizing agent.

Formula 1 below is a chemical formula of PEDOT and dodecyl sulfate dopant constituting the PEDOT film dopedyl sulfate doped according to the present invention.

The dodecyl sulfate content in the dodecyl sulfate doped PEDOT film according to the present invention may range from 5 to 50%, preferably from 20 to 45%, more preferably from 30 to 40% have.

The dodecyl sulfate-doped PEDOT film according to the present invention has excellent electrical conductivity properties that can be applied as an electrode of an electronic device, may be 5,500 S / cm or more, preferably 9,000 S / cm or more, and more preferably It can be 10,000S / cm or more.

The dodecyl sulfate-doped PEDOT film according to the present invention has a light transmittance excellent enough to be applied to a display, and may have a light transmittance of 90% or more at a thickness of about 20 nm for a wavelength of 550 nm.

The dodecyl sulfate-doped PEDOT film according to the present invention has excellent mechanical properties to be applicable to flexible electronic devices. For example, even after performing 300,000 bending cycles, the electrical resistance change may be 9% or less. In addition, the electrical resistance increase may be less than 10% even after pulling the PEDOT film on both sides to increase it by about 30%.

In addition, the dodecyl sulfate-doped PEDOT film according to the present invention may have excellent water-resistant properties such that it can be applied to bio devices. For example, when measuring sheet resistance in a state of being immersed in deionized water for a long time, an increase in electrical resistance may be 5% or less even after immersion for 20 days.

1 and 2 are diagrams and flowcharts for explaining a method of forming a dopedyl sulfate doped PEDOT film according to the present invention, respectively.

Referring to Figures 1 and 2, dodecyl sulfate doped PEDOT film forming method according to the present invention, the step of coating the oxide film on the substrate (S11), forming a PEDOT film by a gas phase polymerization method (S12) and a washing / drying step (S13).

First, the step of coating the oxidant film on the substrate (S11) is a step of coating the oxidizing agent acting as a catalyst for forming the PEDOT film on the substrate. The oxidizing agent coating may be performed by a spin coating method in which a solution containing an oxidizing agent is discharged on a surface of a substrate supported on a spin head, and a uniform oxidizing film is formed by rotating the spin head at high speed.

As the oxidizing agent, a dodecyl sulfate metal salt of the formula M _x (DS) _y can be used. Here, DS is dodecyl sulfate, M is a metal, and may be Fe, Cr, Co, Ni, Mn, V, Rh, Au, Cu, Mo, but is not limited thereto. For example, Fe (DS) ₃ may be used as the oxidizing agent. The present invention can form a PEDOT film dopedyl sulfate doped by forming a PEDOT film by a gas phase polymerization method using a dodecyl sulfate metal salt as an oxidizing agent. In addition, by using dodecyl sulfate metal salt as an oxidizing agent, it is possible to form a high-quality PEDOT film with few defects without using an inhibitor.

Next, in step S12, the substrate coated with the oxidizing film is mounted in the gas phase polymerization chamber. In this case, as shown in FIG. 1, the oxidant film may be mounted on the upper side of the chamber so that it faces downward. A container containing EDOT monomer and water is disposed at the bottom of the chamber, and vaporized EDOT monomer and water are configured to reach the substrate. A PEDOT film is formed on the substrate by a gas phase polymerization method having such a configuration. At this time, the temperature inside the chamber may be controlled by circulating temperature-controlled hot water through a flow path formed in the chamber wall, and a temperature sensor for measuring the temperature may be installed inside the chamber. In FIG. 1, although the substrate is shown mounted on the top of the chamber, the substrate may be mounted on the bottom of the chamber.

The substrate on which the PEDOT film is formed is unloaded in the gas phase polymerization chamber to proceed with washing and drying (step S13). The washing may be to remove excess oxidizing agent and EDOT monomer remaining on the film surface, and may proceed with ethanol. After washing, it can be dried at about 70 ° C. for 1-2 hours to remove the washing solution.

3 is a flowchart illustrating a method for preparing a dodecyl sulfate metal salt oxidizing agent according to an embodiment of the present invention.

Referring to FIG. 3, first, a dodecyl sulfate metal salt is precipitated by a recrystallization method (step S21). Here, the recrystallization method may be a method of depositing a dodecyl sulfate metal salt by adding a metal compound (eg, metal chloride) to a solution in which dodecyl sulfate is dissolved. At this time, the metal compound may be added to the solution in which the dodecyl sulfate is dissolved in the form of an aqueous solution, and the solution may be added while stirring to uniformly mix.

Step S21 may further include a step of removing impurities by a centrifugation method. For example, precipitates obtained by adding a metal compound to a dodecyl sulfate solution may contain impurities. Dissolve the precipitates by dissolving these precipitates in methanol or the like and centrifuging to remove undissolved impurities. The final dodecyl sulfate metal salt precipitate can be obtained from the solution from which impurities have been removed.

The following is a step of washing the precipitated dodecyl sulfate metal salt (step S22) and vacuum freeze drying (step S23). Washing may be repeatedly performed using deionized water, and vacuum freeze drying may be performed under a reduced pressure atmosphere.

4 is a flowchart illustrating in more detail a method of manufacturing a Fe (DS) ₃ oxidizing agent according to an embodiment of the present invention.

Referring to FIG. 4, first, sodium dodecyl sulfate (SDS) is dissolved in deionized water (DI water) to prepare an SDS solution (step S31). At this time, it can be dissolved while stirring until a transparent SDS solution is obtained.

Next is the step of adding FeCl ₃ to the SDS solution (step S32). FeCl ₃ can be added to the SDS solution in the form of an aqueous solution.

Next, the precipitate generated in the SDS solution by adding FeCl ₃ is dissolved in methanol to prepare a methanol solution (step S33). The precipitate can be dissolved in methanol once repeatedly washed with deionized water, and the methanol solution can be centrifuged at high speed to remove undissolved impurities.

Deionized water is added to the methanol solution from which impurities have been removed to precipitate Fe (DS) ₃ recrystallization (step S34). The precipitated Fe (DS) ₃ is repeatedly washed and then dried by a vacuum freeze-drying method, and drying is preferably performed for 2 days or more.

Hereinafter, the present invention will be described in more detail based on specific examples.

1. Experimental method

(1) Preparation of Fe (DS) ₃ oxidizing agent

10.2520 g of sodium dodecyl sulfate (SDS) was dissolved in DI water at 40 ° C. and stirred until it became transparent to obtain a 0.148 mol / L SDS solution. While stirring the SDS solution, 0.197 mol / L FeCl ₃ aqueous solution was slowly added so that the molar ratio between SDS and FeCl ₃ was 3: 1. The generated precipitate was repeatedly washed 10 times or more with deionized water, dissolved in 45 ml methanol, and centrifuged at 5000 rpm to remove undissolved impurities. 200 ml deionized water was added while slowly stirring the methanol solution from which impurities had been removed. Fe (DS) ₃ precipitated by recrystallization from the solution was repeatedly washed 5 or more times, and then vacuum freeze-dried for 2 days or more.

(2) PEDOT film formation

After various types of substrates such as a silicon substrate and a PET substrate on which a thermal oxide film was formed were ultrasonically cleaned in ethanol for 30 minutes, a solution containing 10 wt% to 60 wt% of the oxidizer was spin coated to form an oxidant film on the substrate.

After the oxidant-coated substrate was mounted on the gas phase polymerization chamber with the oxidant film facing downward, the EDED monomer and water provided in the chamber were vaporized to form a PEDOT film on the substrate. At this time, the temperature of the chamber was adjusted to 50 ° C by circulating hot water on the chamber wall, and the chamber temperature was monitored by a temperature sensor provided inside the chamber. After washing with ethanol to remove excess oxidizing agent and EDOT monomer, ethanol was removed by drying under reduced pressure at 70 ° C. for 1 hour.

(3) Characterization

The thermal stability of Fe (DS) ₃ was analyzed by differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA).

The morphology of the PEDOT film was analyzed using a field emission scanning electron microscope (FE-SEM) and an atomic force microscope (AFM). The sheet resistance (R) of the PEDOT film was measured using a four-point probe, and then the electrical conductivity was calculated using the film thickness measured with FE-SEM.

In addition, PEDOT film analysis using X-ray photoelectron spectroscopy (XPS), The Raman spectroscopy, Grazing incidence X-ray diffraction, etc. was performed.

2. Fe (DS) ₃ oxidizer properties analysis results

Table 1 shows the results of XPS analysis of the prepared Fe (DS) ₃ oxidizing agent. The concentration of Cl (2p) was shown as 0%, and it was confirmed that a high-purity oxidant was obtained in which Cl ions were completely removed by the method for preparing an oxidant according to the present invention.

ingredient	Content (atomic%)
C (1s)	66.41
Cl (2p)	0.00
Fe (2p)	1.98
S (2p)	8.17
O (1s)	23.43

5 is a result of TGA analysis. As can be seen from the weight loss graph of FIG. 5, several different gradients are observed in the range of 30-350 ° C. The first weight loss in the first region (Region 1) in the range of 30 to 126 ° C is due to the release of water molecules contained in the oxidizing agent, and based on the weight loss (10.2%) in the temperature range, the present invention The exact chemical formula of the oxidizing agent prepared according to the example is calculated as Fe (DS) ₃ · 5.3H ₂ O.

6 is a DSC analysis result of the oxidizing agent prepared according to an embodiment of the present invention. It is confirmed that an endothermic peak related to water molecule release appears at about 48 ° C. The peak appearing at about 76 ° C is due to the formation of a typical intermediate liquid crystalline phase, and the endothermic reaction starting at about 97 ° C and showing a peak at 116 ° C is chemical transformation of Fe (DS) ₃ It is estimated to be due to. The results of observing the effect of these chemical changes are shown in FIG. 7. When the Fe (DS) ₃ oxidizing agent prepared according to the embodiment of the present invention is heat treated at 100 ° C. for 10 minutes, it changes from brown to black, and is dissolved in methanol before heat treatment to become a transparent brown solution, while an opaque suspension after heat treatment It was observed that this was formed.

The strong endothermic peak shown at 140 ° C is judged to be due to chemical decomposition of the compound.

According to the results of the thermal analysis, it can be seen that the Fe (DS) ₃ oxidizing agent is chemically stable at a temperature of about 76 ° C. or less, which is controlled so that the manufacturing process temperature of the Fe (DS) ₃ oxidizing agent does not exceed about 76 ° C. It means that it is desirable. In the embodiment of the present invention, vacuum freeze-drying is performed without the usual high-temperature heat treatment for drying the Fe (DS) ₃ oxidizing agent, and it is related to this, and finally, through vacuum freeze-drying, a PEDOT film is formed by gas phase polymerization. It was possible to manufacture a high-quality Fe (DS) ₃ oxidizing agent that could be utilized.

3. PEDOT film analysis results

(1) Morphology analysis result

The results of analyzing the morphology of the PEDOT film formed by the gas phase polymerization method using Fe (DS) ₃ oxidizing agent according to an embodiment of the present invention by AFM and FE-SEM are shown in FIG. 8. 8A to 8D are results of forming a PEDOT film on a PET substrate, FIG. 8E a PI substrate, and FIG. 8F a SiO ₂ substrate.

According to the AFM analysis result of FIG. 8A, the surface roughness of the PEDOT film was a root-mean-square (RMS) roughness, and a flat surface of about 1.87 nm was obtained. In addition, according to the FE-SEM photograph, a high-density smooth surface was observed regardless of the substrate type, and it was confirmed that uniform PEDOT films were grown on all the substrates.

(2) Analysis of electrical and optical properties

9 is a result of measuring the electrical conductivity of a PEDOT film formed by a gas phase polymerization method using Fe (DS) ₃ oxidizing agent according to an embodiment of the present invention. 9 shows the results of using a PET substrate as a substrate, but similar electrical conductivity characteristics were obtained regardless of the substrate type. 9A to 9C show changes in electrical conductivity according to polymerization time, polymerization temperature, and oxidizer concentration, respectively.

9A shows a change in electrical conductivity according to polymerization time at a polymerization temperature of 40 ° C. and an oxidizer concentration of 50 wt%. As the polymerization time increases, the film thickness increases, but the electrical conductivity decreases. Therefore, within the experimental range, 30 minutes of polymerization time can be optimally selected.

9B shows the change in electrical conductivity according to the polymerization temperature at a polymerization time of 30 minutes and an oxidizer concentration of 50%. As the polymerization temperature increases from 30 ° C to 60 ° C, the film thickness continuously increases, especially at 50 ° C or more. Although an increase appears, it can be seen that the electrical conductivity has a maximum value at 50 ° C. That is, the polymerization temperature within the experimental range can be selected to 50 ℃.

9C shows the results of experiments of electrical conductivity according to the concentration of the oxidant at an optimally selected polymerization time of 30 minutes and a polymerization temperature of 50 ° C. As the concentration of the oxidizing agent increased from 10% to 30%, the electrical conductivity also continued to increase, but at 30% or more, it was found to start decreasing again. Therefore, the optimal oxidant concentration can be selected as 30%, and the electrical conductivity at this time was 10,307 ± 500S / cm. Since the highest electrical conductivity of the PEDOT film by the gas phase polymerization method reported so far is 5,400S / cm of the tosylate-doped PEDOT film, the electrical conductivity of the PEDOT film formed according to the embodiment of the present invention is the electrical conductivity of the prior art. It was almost doubled. In addition, 30% of the oxidizing agent concentration, as well as most of the oxidizing agent concentration range of FIG. 9C, electrical conductivity characteristics superior to conventional electrical conductivity were obtained. Therefore, the high electrical conductivity property of the PEDOT film according to the embodiment of the present invention can be said to be the effect of dodecyl sulfate doping using Fe (DS) ₃ oxidizing agent.

10 is a graph of light transmittance at a wavelength of 550 nm according to the thickness of a PEDOT film formed on a PET substrate. It showed a light transmittance of 87% or more at a thickness of 47 nm or less, and a light transmittance of 90% or more at a thickness of 21.3 nm. The light transmittance is a level that can be sufficiently utilized as a transparent electrode in a display device.

Table 2 shows the electrical and optical properties of the PEDOT film according to the substrate. Regardless of the substrate type, it exhibited high electrical conductivity up to about 10,000 S / cm and high light transmittance of over 90%.

Board	Thickness (nm)	Electrical conductivity (Scm -1 )	Light transmittance at 550nm wavelength (%)
PET	21.3	10,110 ± 500	90.8
PI	22.8	9,856 ± 500	90.6
SiO 2 -wafer	21.0	10,307 ± 500	NA

(3) Doping level analysis result

11 is a result of XPS analysis of the Fe (DS) ₃ oxidizer film (FIG. 11A) and the PEDOT film (FIG. 11B) formed thereon. 11A, the two XPS bands appearing between 166eV and 172eV in FIG. 11B are the S2p band of the sulfur atom of the dodecyl sulfate (DS) component, and the two XPS bands appearing between 162eV and 166eV in FIG. 11B. It is the S2p band of the sulfur atom in PEDOT. S2p peaks by dodecyl sulfate (DS) appear at 167.65 eV and 169.13 eV in PEDOT, and are different from 169.5 eV and 170.5 eV in Fe (DS) ₃ . The doping level of dodecyl sulfate (DS) calculated from the ratio of XPS peaks in FIG. 11B was about 37%.

(4) Results of mechanical properties analysis

12 (a) is a result of measuring a change in electrical resistance after bending a PEDOT film sample formed on a PET substrate. It can be seen that even when the bending radius of bending reaches 0 mm, there is little change in electrical resistance.

12 (b) shows the results of measuring the electrical resistance change while repeating the bending cycle, and the banding frequencies were 0.5 Hz and 2 Hz. It was confirmed that there was little change in electrical resistance even after 10,000 bending cycles regardless of frequency. In addition, it was confirmed that even after 200,000 bending cycles, the electrical resistance change was only 7 to 10%, and specifically, even after 300,000 bending cycles, the electrical resistance change was less than 9%.

12 (c) shows the results of stretching test after forming the PEDOT film on the polyurethane substrate. According to FIG. 12 (c), even when the PEDOT film was pulled on both sides to increase about 30%, the increase in electrical resistance was only 10%.

As described above, it can be seen that the PEDOT film according to the embodiment of the present invention can be applied to various flexible devices such as wearable electronic devices, flexible displays, and foldable batteries due to slight changes in electrical resistance due to bending or stretch.

(5) Stability in aqueous solution

The water-resistant property was analyzed by measuring the change in sheet resistance over time by immersing the PEDOT film according to an embodiment of the present invention in deionized water, and the results are shown in FIG. 13. 50 ohm / sq after initial immersion in deionized water for 20 days at 46.1 ohm / sq. Maintained below, it was confirmed that the water resistance of the PEDOT film according to the embodiment of the present invention is very excellent.

(6) Crystal structure analysis

In-plane XRD (X-ray diffraction) and out-of-plane GIWAXS (Grazing incidence wide angle x-ray scattering) analysis to analyze the crystal structure of the dodecyl sulfate doped PEDOT thin film according to an embodiment of the present invention And the results are shown in FIGS. 14 (a) and 14 (b), respectively.

The in-plane XRD of FIG. 14 (a) shows the crystallinity on the xy plane parallel to the surface of the PEDOT film, and the peak present at 2θ = 26.72 ° is the π-π stacking between the PEDOT backbones (π-π stacking) means that the distance is 0.34nm. In addition, peaks at 2θ = 19.792 ° and 36.256 ° are peaks in the 010 and 020 directions with periodicities of 0.45 nm and 0.49 nm, respectively, and the average xy direction packing distance of dodecyl sulfate anion dopant molecules is about 0.47. nm.

The out-of-plane GIWAXS result of FIG. 14 (b) shows crystallinity in the z-axis direction, which is the thickness direction of the PEDOT film, and a peak of 2θ = 6.7 ° has a PEDOT crystal lamellar interlayer distance along the 100 plane direction of 1.32 nm. Shows that

 According to the structure prediction based on the above crystal structure analysis result, the structure of the PEDOT film dopedyl sulfate doped according to an embodiment of the present invention is shown in FIG. 15.

In the xy plane parallel to the surface of the PEDOT film, the direction in which the PEDOT main chain is lined is the x-axis direction and the direction perpendicular thereto is the y-axis direction, and the thickness direction of the PEDOT film is the z-axis direction, FIG. 15 (a) is x The sectional view of the film as viewed in the axial direction, FIG. 15 (b) is a perspective view of the film as viewed in the x-axis direction, and FIG. 15 (c) is the perspective view of the film as viewed in the y-axis direction. 15 may be a structure inside one grain (grain) in the film. 15 (a) shows that the PEDOT molecules are made of a lamellar structure, and the lamellar interlayer distance (the distance between the PEDOT main chain axes) is 1.32 nm. This is supported by the out-of-plane GIWAXS results of Fig. 14 (b). Considering the width of the PEDOT molecule here, the effective space between the PEDOT molecular layers is calculated to be 0.57 nm, which is almost identical to the theoretical width of 0.56 nm with two dodecyl sulfate molecules stacked. That is, the PEDOT film according to an embodiment of the present invention may have a lamellar structure in which two dodecyl sulfate molecules are doped between PEDOT molecular layers.

In the case of a structure doped with two dodecyl sulfate molecules, hydrophobic ethylene (-CH2CH2-) groups periodically exposed above and below the PEDOT lamellar layer have a very close van der Waals interaction with the dodecyl group of the dopant molecule. As it can, it is also advantageous in terms of energy.

15 (b) is a perspective view of the film as viewed in the x-axis direction, while FIG. 15 (a) shows only one layer in the x-axis direction, while FIG. 15 (b) shows two layers in the x-axis direction ( It is a drawing where two layers are overlapped. According to FIG. 15 (b), two PEDOT main chains form two lamellar layers, and each lamellar layer includes a total of 12 EDOTs. That is, there are a total of 24 EDOT molecules on FIG. 15 (b), and 8 of the dodecyl sulfate molecules are arranged between the lamellar layers. This is in good agreement with the dodecyl sulfate doping level calculated from XPS analysis, about 37%.

FIG. 15 (c) is a perspective view of the film as viewed from the y-axis direction, showing a crystal structure in which a total of six PEDOT main chains are stacked π-π to form two lamella layers at the top and bottom. Here, the distance of π-π stacking between PEDOT main chains is 0.34 nm, and the distance between hydrocarbon chains of dodecyl sulfate dopant molecules is regularly placed at 0.47 nm. This is supported by the in-plane XRD results of Fig. 14 (a).

According to such a crystal structure, it can be seen that the dodecyl sulfate located above and below the PEDOT crystal layer is very efficiently doped, and at the same time, a long hydrocarbon chain has a structure that densely surrounds the crystal layer. Such a structure well describes the high electrical conductivity of the PEDOT film dopedyl sulfate doped according to an embodiment of the present invention, very flexible elasticity, and excellent mechanical durability. In addition, according to a crystal structure in which a hydrocarbon chain having high hydrophobicity surrounds each PEDOT crystal layer densely, it is expected to be able to maintain a very good film quality and electrical conductivity in an aqueous solution or even at high humidity, according to an embodiment of the present invention. It is also in good agreement with the excellent aqueous solution stability results of the dodecyl sulfate doped PEDOT film.

In the embodiment of the present invention, the dopant anion is limited to dodecyl sulfate, but according to the crystal structure of FIG. 15, it can be expected that the dopant anion may be slightly shorter or slightly longer in hydrocarbon length than dodecyl sulfate. . Indeed, according to the experiment of the present inventors, as a result of applying dopant anions having a hydrocarbon chain length of 8C to 18C, there was a difference in degree, but it was possible to obtain properties superior to the PEDOT film reported in the related art. That is, it should be understood that a PEDOT film doped with a dopant anion of CH ₃ (CH ₂ ) _n SO ₄ (n = 7 to 17) is also included within the scope of the present invention.

Although described above with reference to the limited embodiments and drawings, it is only an embodiment, it will be apparent to those skilled in the art that various modifications can be implemented within the scope of the technical idea of the present invention.

Therefore, the protection scope of the present invention should be defined by the description of the claims and their equivalents.

Claims (24)

1. PEDOT film containing dodecyl sulfate as dopant.
2. According to claim 1,

   The PEDOT film is a PEDOT film, characterized in that formed by a gas phase polymerization method using a dodecyl sulfate metal salt as an oxidizing agent.
3. According to claim 2,

   The dodecyl sulfate metal salt is a PEDOT film, characterized in that Fe (DS) ₃ .
4. The method according to any one of claims 1 to 3,

   PEDOT film, characterized in that the content of the dodecyl sulfate dopant is in the range of 5 to 50%.
5. The method according to any one of claims 1 to 3,

   PEDOT film characterized in that the electrical conductivity of 5,500S / cm or more.
6. The method of claim 5,

   PEDOT film, characterized in that the electrical conductivity of 10,000S / cm or more.
7. The method according to any one of claims 1 to 3,

   PEDOT film characterized in that it exhibits a light transmittance of 90% or more for a wavelength of 550nm at a thickness of 20nm.
8. The method according to any one of claims 1 to 3,

   PEDOT film characterized in that the electrical resistance change after 300,000 bending cycles is 9% or less, or the electrical resistance change after 30% tensile is 10% or less.
9. The method according to any one of claims 1 to 3,

   PEDOT film characterized in that the change in electrical resistance is 5% or less even after immersion in deionized water for 20 days or more.
10. The method according to any one of claims 1 to 3,

    PEDOT film, characterized in that the lamellar structure dopedyl sulfate molecule doped between the PEDOT molecular layer.
11. The method of claim 10,

    PEDOT film, characterized in that two dodecyl sulfate molecules are doped between the PEDOT molecular layer.
12. An electronic device comprising the PEDOT film according to any one of claims 1 to 3.
13. The method of claim 12,

    The PEDOT film is an electronic device characterized in that it is included as an electrode.
14. Coating an oxidant film containing dodecyl sulfate metal salt on a substrate;

    Forming a PEDOT film on the substrate coated with the oxidizer film by gas phase polymerization;

    Washing and drying the PEDOT film;

    PEDOT film manufacturing method comprising a.
15. The method of claim 14,

    The dodecyl sulfate metal salt PEDOT film production method characterized in that it comprises Fe (DS) ₃ .
16. The method of claim 14 or 15,

    PEDOT film production method characterized in that the inhibitor is not used.
17. As a method for producing an oxidizing agent for use in preparing a PEDOT film by a gas phase polymerization method,

    Depositing a metal salt of dodecyl sulfate by a recrystallization method;

    Washing the precipitated dodecyl sulfate metal salt; And

    Vacuum freeze-drying;

    Oxidizing agent production method comprising a.
18. The method of claim 17,

    The dodecyl sulfate metal salt is a method of manufacturing an oxidizing agent comprising Fe (DS) ₃ .
19. The method of claim 18,

    The step of depositing the dodecyl sulfate metal salt by the recrystallization method,

    A method of manufacturing an oxidizing agent further comprising the step of removing impurities by centrifugation.
20. The method of claim 18,

    The step of depositing the dodecyl sulfate metal salt by the recrystallization method,

    Preparing a sodium dodecyl sulfate solution;

    Adding FeCl ₃ to the sodium dodecyl sulfate solution;

    Method for producing an oxidizing agent comprising a.
21. The method of claim 20,

    Preparing a methanol solution by dissolving the precipitate generated in the sodium dodecyl sulfate solution in methanol by adding FeCl ₃ ;

    The method of claim 1, further comprising the step of depositing recrystallization of Fe (DS) ₃ by adding deionized water to the methanol solution.
22. A PEDOT film having a lamellar structure in which one or more anionic molecules are doped between PEDOT molecular layers,

    The anionic molecule is a CH ₃ a hydrocarbon chain length 8C to _{18C (CH 2) n SO 4} - (n = 7 ~ 17) PEDOT film, characterized in that the dopant anion.
23. The method of claim 22,

    PEDOT film, characterized in that there are two anionic molecules doped between the PEDOT molecular layer.
24. The method of claim 22,

    When the direction in which the PEDOT main chain is lined is the x-axis direction and the direction perpendicular to this is the y-axis direction

    The PEDOT molecules are π-π stacked in the y-axis direction,

    The doped anion molecules are PEDOT film, characterized in that periodically arranged in the upper and lower parts of the π-π stacked PEDOT molecules.

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